The extracellular matrix glycoproteins laminin and entactin are synthesized and secreted by epithelial cells. These glycoproteins appear to mediate the adhesion of epithelial cells to the basement membranes. The objectives of this proposal are (a)\to attempt to elucidate the structures of the region of the glycoproteins responsible for cell adhesion, (b)\to obtain information on the receptor sites on the plasma membranes that bind the glycoproteins and (c)\to explore the specificity of interaction between the glycoproteins and receptors from different sources. An extracellular membrane complex elaborated by mouse endodermal cells will be employed in the initial adhesion studies to be performed; cell lines that will be studied include human mammary MCF-7 tumor cells, African Green Monkey kidney BSC cells and rat hepatoma cells. Monoclonal antibodies developed from rat spleen cells against the GP-2 subunit of laminin and polyclonal rabbit antibodies against GP-1, GP-2 and entactin will be used as probes. The long-range objective of the project is an understanding of the subtle interactions between cells and their underlying matrix in metastasis, embryogenesis and cell differentiation.